The invention relates on the one hand to a method for contactless tapping of communication signals that are exchanged between two communication units, wherein the communication signals are transmitted as voltage signals on a line of a multi-core cable. The two communication units are in particular a sensor on the one hand and an actuator and a digital evaluation or control unit on the other hand. Furthermore, the invention relates to an assembly for performing such a method.
In the practice of automation technology there is a continuous demand to “wiretap” the data traffic on a signal line, for example for analyzing the communication between the master and a slave of a fieldbus system. A separation of the signal line at the corresponding point here is usually not desirable, because that would be associated with an at least temporary shutdown of the plant. In the prior art, current clamps and the like are known, i.e. a clamp-like tool, which engages around the cable and detects the signals according to the transformer principle without the need to interrupt the signal line. However, in the case of a multi-core cable in which the single line cannot be separated and thus be gripped, the tap is no longer possible in this manner or the detected signals are so weak that a reconstruction of the original signals yields no satisfactory result. Incidentally, in this way only current levels and no voltage signals can be detected.
It is the object of the invention to be able to tap the voltage signals even in multi-core cables without having to interrupt the line.